The invention relates to displaying an image from a first video channel and an image from a second video channel within one combined picture.
In order to display an image from a first video channel and an image from a second video channel within one combined picture, a known approach is to feed a first video signal and a second video signal to a multiplexer, wherein the first video signal contains video information for a first image to be displayed in a first active region of the combined picture, and the second video signal contains video information for a second image to be displayed in a second active region of the combined picture. In the known method, the multiplexer generates an output video signal from the first and second video signals which may be utilized to display the combined picture using a conventional display device such as a monitor.
The combined picture is built up line-by-line, that is, the video information for adjacent pixels within the combined picture is present in the output signal in temporally sequential form. Similarly, the first and second video signals contain video information for adjacent pixels in temporally sequential form. For each pixel whose video information is contained in the output signal, the multiplexer decides whether the pixel lies within the first or second active regions of the combined picture, or outside of these active regions. If the pixel lies within the first active region, the multiplexer transmits the first video signal, or the video information from this video signal, to the output to generate the output signal. If the pixel lies within the second active region, the multiplexer transmits the second video signal to the output, and if the pixel lies outside the first and second active regions the multiplexer transmits a video signal for a background image to the output. The sequential values of the output signal which contains the line-by-line information for the combined picture are thus obtained for the background image from the first or second video signals depending on the position of a given pixel within the combined picture.
To enable the decision to be made as to whether a given pixel lies within or outside of the first or second active regions, the multiplexer is fed control signals which contain information on the position and dimensions of the active regions.
If the first and second active regions overlap, a priority signal is referenced to decide whether to take the video information for a given pixel of the overlap region from the first or second video signals, the priority signal determining which of the video signals to use to display the pixels of the overlap region, that is, which of the two images must be in the foreground while the other of the two images is partially or completely covered. Given two images to be displayed, the priority signal may assume two different values such that if there is a change in the priority signal, the image previously displayed in the background may now move to the foreground.
The known method permits only the display of the video information from one of the video signals in the overlap region.
Therefore, there is a need for a system and a method of displaying a first and a second image within a combined picture which allows for the display of video information from the first and second video signals within the overlap region, and in which cross-fading from the first to the second image within the overlap region is possible when the image to be displayed in the foreground changes.